GaN device processing

Recent progress in the development of dry and wet etching techniques, implant doping and isolation, thermal processing, gate insulator technology and high reliability contacts is reviewed. Etch selectivities up to 10 for InN over AlN are possible in Inductively Coupled Plasmas using a Cl-2/Ar chemistry, but in general selectivities for each binary nitride relative to each other are low (less than or equal to 2) because of the high ion energies needed to initiate etching. Improved n-type ohmic contact resistances are obtained by selective area Si+ implantation followed by very high temperature (>1300 degrees C) anneals in which the thermal budget is minimized and AlN encapsulation prevents GaN surface decomposition. Implant isolation is effective in GaN, AlGaN and AlInN, but marginal in InGaN. Candidate gate insulators for GaN include AlN, AlON and Ga(Gd)O-x, but interface state densities are still to high to realize state-of-the-art MIS devices.